A waning crescent moon—sometimes called an old moon—is an intermediate phase of the lunar cycle that starts right after the third quarter moon and lasts until it becomes a new moon.
Meaning of a waning crescent moon
A waning crescent moon consists of two terms: waning and crescent.
“Waning” means decreasing or shrinking. After a third quarter moon, the illuminated area of the moon decreases day by day until it becomes a new moon. That’s why it’s called a waning moon.
The illuminated area of a waning crescent moon decreases from 50% to 0%.
“Crescent” means curved sickle shape. The moon looks like a curved sickle shape between a third quarter moon and a new moon. That’s why it’s called a crescent moon.
So a waning crescent moon indicates the shape of the moon.
Rise and set time of a waning crescent moon
A waning crescent moon rises after midnight (between midnight and sunrise), reaches its highest point in the sky (overhead point) in the morning, and sets in the afternoon (between noon and sunset).
Please remember, a waning crescent moon does not rise and set at the same time every day. On consecutive days, a waning crescent moon rises and sets about 50 minutes later.
Best time to see a waning crescent moon
You’ll find a waning crescent moon in the eastern sky before sunrise around two to three days before a new moon.
A waning crescent moon is difficult to see in the daytime as it disappears in the sun’s glare due to its thin sickle shape.
Duration of a waning crescent moon
The moon takes about 29.5 days to complete a lunar cycle.
Now, a lunar cycle has eight phases in total. These are the new moon, waxing crescent moon, first quarter moon, waxing gibbous moon, full moon, waning gibbous moon, third quarter moon, and waning crescent moon.
Four primary phases (new moon, first quarter, full moon, and third quarter) have no duration as they occur at a specific moment in time.
So the duration of four intermediate phases (waxing crescent, waxing gibbous, waning gibbous, and waning crescent) is 29.5 days in total.
So the duration of a waning crescent moon is about 29.5/4 = 7.38 days.
Orientation of a waning crescent moon
A waning crescent moon appears as a curved sickle shape in the sky from anywhere in the world. Its percentage of illumination is also the same. However, it looks opposite in opposite hemispheres.
In the Northern Hemisphere, the illuminated part appears on the left side, and in the Southern Hemisphere, it appears on the right side.
Earthshine on a waning crescent moon
You might see earthshine – the faint beautiful glow on the unlit part of a waning crescent moon. Look for them in the eastern sky around an hour before sunrise.
The phases of the moon
The moon goes through phases as it orbits Earth. Follow the links below to understand the phases of the moon.
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